Scientists: Wind, Drought Worsen Fires, Not Bad Management
VOA News
November 12, 2018 4:44 PM Associated Press (source)
Scientists: Wind, Drought Worsen Fires, Not Bad Management
科學家澄清：風勢和乾旱加劇加州大火火勢，並非管理不善所致
November 12, 2018 4:44 PM
Associated Press
WASHINTON —
Both nature and humans share blame for California's devastating wildfires, but forest management did not play a major role, despite President Donald Trump's claims, fire scientists say.
Nature provides the dangerous winds that have whipped the fires, and human-caused climate change over the long haul is killing and drying the shrubs and trees that provide the fuel, experts say.
"Natural factors and human-caused global warming effects fatally collude" in these fires, said wildfire expert Kristen Thornicke of the Potsdam Institute for Climate Impact Research in Germany.
Multiple reasons explain the fires' severity, but "forest management wasn't one of them," University of Utah fire scientist Philip Dennison said.
Trump tweeted on Saturday: "There is no reason for these massive, deadly and costly forest fires in California except that forest management is so poor. Billions of dollars are given each year, with so many lives lost, all because of gross mismanagement of the forests."
The death toll from the wildfire that incinerated the town of Northern California town of Paradise and surrounding areas climbed to 29, matching the mark for the deadliest single blaze in California history. Statewide, the number of fire dead stood at 31, including two victims in Southern California.
One reason that scientists know that management isn't to blame is that some areas now burning had fires in 2005 and 2008, so they aren't "fuel-choked closed-canopy forests," Dennison said.
In those earlier fires, Paradise was threatened but escaped major damage, he said. In the current blazes, it was virtually destroyed.
The other major fire, in Southern California, burned through shrub land, not forest, Dennison said.
"It's not about forest management. These aren't forests," he said.
The dean of the University of Michigan's environmental school, Jonathan Overpeck, said Western fires are getting bigger and more severe. He said it "is much less due to bad management and is instead the result of our baking of our forests, woodlands and grasslands with ever-worsening climate change."
Wildfires have become more devastating because of the extreme weather swings from global warming, fire scientists said. The average number of U.S. acres burned by wildfires has doubled over the level from 30 years ago.
As of Monday, more than 13,200 square miles (34,200 square kilometers) have burned. That's more than a third higher than the 10-year average.
From 1983 to 1999, the United States didn't reach 10,000 square miles burned annually. Since then, 11 of 19 years have had more than 10,000 square miles burned, including this year. In 2006, 2015 and 2017, more than 15,000 square miles burned.
The two fires now burning "aren't that far out of line with the fires we've seen in these areas in recent decades," Dennison said.
"The biggest factor was wind," Dennison said in an email. "With wind speeds as high as they were, there was nothing firefighters could do to stop the advance of the fires."
These winds, called Santa Ana winds, and the unique geography of high mountains and deep valleys act like chimneys, fortifying the fires, Thornicke said.
The wind is so strong that fire breaks — areas where trees and brush have been cleared or intentionally burned to deprive the advancing flames of fuel — won't work. One of the fires jumped over eight lanes of freeway, about 140 feet (43 meters), Dennison said.
Southern California had fires similar to the Woolsey fire in 1982, when winds were 60 mph, but "the difference between 1982 and today is a much higher population in these areas. Many more people were threatened and had to evacuated, [sic]" Dennison said.
California also has been in drought for all but a few years of the 21st century and is now experiencing its longest drought, which began on Dec. 27, 2011, and has lasted 358 weeks, according to the U.S. Drought Monitor. Nearly two-thirds of the state is abnormally dry.
The first nine months of the year have been fourth-warmest on record for California, and this past summer was the second-hottest on record in the state.
Because of that, there are 129 million dead trees, which provide fuel for fires, Thornicke said.
And it's more than trees. Dead shrubs around the bottom of trees provide what is called "ladder fuel," offering a path for fire to climb from the ground to the treetops and intensifying the conflagration by a factor of 10 to 100, said Kevin Ryan, a fire consultant and former fire scientist at the U.S. Forest Service.
While many conservatives advocate cutting down more trees to prevent fires, no one makes money by cutting dead shrubs, and that's a problem, he said.
Local and state officials have cleared some Southern California shrub [sic], enough for normal weather and winds. But that's not enough for this type of extreme drought, said Ryan, also a former firefighter.
University of Alberta fire scientist Mike Flannigan earlier this year told The Associated Press that the hotter and drier the weather, the easier it is for fires to start, spread and burn more intensely.
It's simple, he said: "The warmer it is, the more fire we see."
For every 1.8 degrees Fahrenheit that the air warms, it needs 15 percent more rain to make up for the drying of the fuel, Flannigan said.
Federal fire and weather data show the years with the most acres burned were generally a degree warmer than average.
"Everyone who has gardened knows that you must water more on hotter days," Overpeck said. "But, thanks in part to climate change, California isn't getting enough snow and rain to compensate for the unrelenting warming caused by climate change. The result is a worsening wildfire problem.
儘管美國總統川普（Trump）稱森林管理不當是造成加州（California）毀滅性（devastating）野火的主因，火災學家卻認為自然與人為因素均難辭其咎。
專家說，大自然帶來促發(whip)火災的危險風勢，而人為的氣候變遷(climate change)就長期來說(over the long haul)，正逐步扼殺並使灌木叢(shrub)枯竭，而此舉將產生引火源(fuel)。
這些火災中，「自然因素和人為的全球暖化效應致命地(fatally)串連(collude)在一起」，位於德國的波茲坦氣候衝擊影響研究所（Potsdam Institute for Climate Impact Research，PIK）的野火專家克莉斯汀．索爾尼克（Kristen Thornicke）說。
多重因素解釋了為何這些火災如此猛烈(severity)，但「森林管理並非其中之一。」美國猶他大學（University of Utah）的消防科學家菲利普．丹尼森（Philip Dennison）說。
川普在星期六（編按：2018 年 11 月 10 日）的推文中寫道：「除了森林管理不善外，沒有別的理由能解釋這場發生在加州，大規模造成人民傷亡與財物損失的森林火災。儘管每年投入數十億的資金，依舊奪走無數條性命，這全是因嚴重的(gross)森林管理不當所致。」
這場將北加州天堂鎮（town of Paradise）和周圍區地區作灰燼(incinerate)的野火釀成 29 人死亡(toll)，名符其實地成為加州史上最致命的一場烈焰(blaze)。死於火災的人數遍及全州達31 人，包含 2 名南加州的受害者。
科學家認為不應責難管理方式的原因之一在於有些起火地區早在 2005 和 2008 年就發生過火災，所以它們並不是那種「會使燃料無法燃燒且密閉的樹冠(canopy)森林。」丹尼森說。
他說，起初的幾場火災中，天堂鎮雖岌岌可危但有幸免於重大損失。日前的大火中卻讓它近乎毀滅。
「另一場位在南加州的主要大火把灌木林區燃燒殆盡，未波及森林。」丹尼森說道。
「這並不是林業管理出的問題。它們並不是森林。」他說。
美國密西根大學（University of Michigan）環境學院院長強納森．歐弗佩克表示，美西的火災有越趨擴大且嚴重的情形。他說這「跟管理不善關係不大，而是出自愈形惡化的氣候變遷帶來的高溫烘烤森林、林地(woodland)與草地(grassland)的緣故。」
消防科學家表示，由全球暖化形成的極端氣候使得野火日益險惡。過去 30 年來，美國境內被野火燒毀的平均英畝數已呈現雙倍成長。
迄星期一（編按：2018 年 11 月 12 日）為止，超過 1 萬 3200 平方英里（等同於 3 萬 4200 平方公里）遭焚毀，這已經超過平均 10 年來第三高的紀錄。
從 1983 到 1999 年，美國每年被燒掉的土地面積不足一萬平方英里。然自那時起，19 年中有 11 年每年超過一萬平方英里遭燒毀，包括今年在內。2006 年、2015 年和 2017 年皆有逾 1 萬 5000 平方英里被焚毀。
「目前這兩場火災並未超乎於(out of line with . . .)近幾十年來我們在這些地區目睹的事故」，丹尼森坦言。
「最大的因素在於風勢」，丹尼森在一封電子郵件中寫道。「在風速的助長下，消防員對蔓延的火勢基本上束手無策。」
索爾尼克指出，這些被稱作聖塔安那風（Santa Ana winds）的風勢，與獨特的高山低谷地形如煙囪般地增強(fortify)了火勢。
風勢之強勁連帶使得火勢摧毀為阻擋火舌蔓延，而特別清除並先行燒毀的樹林與灌木叢。其中一場火災甚至翻越近 140 英尺（約 43 公尺）的 8 線道高速公路。
南加州的火災與 1982 年的伍爾西大火（Woolsey fire）極其相似，兩者皆出現在風勢達到 60 英里之際，「但不同之處在於比起 1982 年，現今這些地區的人口大幅成長。更多人備受威脅且必須撤離(evacuate)。」丹尼森說。
加州同時也遭受 21 世紀初幾年的旱災(drought)。美國的乾旱監控（U.S. Drought Monitor）資料顯示，當地目前正飽受有史以來最漫長的乾旱之苦，此旱災自 2011 年 12 月 27 日起至今已長達 358 週，境內近三分之二的地區處於異常(abnormally)乾燥的狀態。
今年頭 9 個月的氣溫是加州史上(on record)的第四高溫，而剛過去的這個夏天亦成為該州有紀錄以來第二炎熱的季節。
「正因如此，有 1 億 2900 萬棵樹木死亡，為野火提供了燃料。」索爾尼克說。
曾在美國林業署（U.S. Forest Service）供職的火災顧問凱文．萊恩（Kevin Ryan）表示，不只樹木遭殃而已，在樹底枯死的矮木叢會形成所謂的「燃點梯」，為火勢從地面向樹頂竄升提供路徑，且擴大火災(conflagration)程度達 10 到 100 倍(by a factor of . . .)。
他說，儘管許多傳統人士(conservative)提倡(advocate)多伐木以避免火災，卻沒有人可藉由砍伐枯矮灌木而獲利，那才是問題所在。
當地和州政府官員已清除部分南加州的灌木叢，使其能應付正常氣候和風勢。但也曾是消防員的萊恩說，這仍不足以因應這種極端型態的乾旱。
加拿大阿爾伯塔大學（University of Alberta）防災學家麥克．弗拉尼根（Mike Flannigan）在今年初告訴美聯社（Associated Press）說，氣候越是炎熱乾燥，越容易引起火災，且蔓延和燃燒的程度亦猛烈(intensely)。
「道理很簡單，」他說：「氣候越溫暖就會有越多火災。」
只要華氏溫度（Fahrenheit）每上升 1.8 度，就需要多 15% 的雨量平衡愈發乾燥的燃點，弗拉尼根說。
聯邦火災與氣象數據顯示，受災面積最廣的年份往往比一般年度的均溫高了一度。
「有栽種經驗的人都知道，在熱天裡必須要澆灌更多的水」，歐弗佩克說，「然而，部分因為(thanks to . . .)氣候變遷的關係，加州缺乏足夠的降雪和降雨來彌補(compensate)氣候變遷造成的持續(unrelenting)暖化。這樣的下場就是更加惡化的野火問題。」
Language Notes
whip [hwɪp] [wɪp] (v) 鞭笞，抽打；猛然挪動（或拿取，拔出等）；迅速作成；然在本文中意指 激起，煽動，有促使之意
over the long haul (prep phr) 以長期來說
shrub [ʃrʌb] (n) 矮樹，灌木
fuel [`fjʊəl] (n) 燃料；刺激因素 * 本字也可作動詞，意指「為 . . . . . . 添加燃料」或「加強；激起」
collude [kə`lud] (v) 共謀；串通；本文中意指兩個因素刻意地連結在一起 * 注意本字重音在第 2 音節
severity [sə`vɛrətɪ] (n) 嚴格；嚴厲；嚴肅；猛烈；凜冽；嚴重，嚴峻 * 注意本字重音在第 2 音節 * severe [sə`vɪr] (a) 非常嚴重的；劇烈的；慘重的
toll [tol] (n) 損失；傷亡人數
incinerate [ɪn`sɪnə͵ret] (v) 燒成灰；焚化；灰化 * 注意本字重音在第 2 音節
blaze [blez] (n) 火焰；火災；熊熊燃燒；強烈的光，光輝 * 本字也可作動詞，意即「熊熊燃燒」或「閃耀；發亮光」
out of line with something (prep phr) 出格；越軌；與 . . . . . . 相差懸殊
conflagration [͵kɑnflə`greʃən] (n) 大火，大火災 * 注意本字重音在第 3 音節
unrelenting [͵ʌnrɪ`lɛntɪŋ] (a) 持續的；未減弱的 * 注意本字重音在第 3 音節；另一常見意思為「堅定不移的；不鬆懈的；不屈不撓的」
Check your vocabulary!
Fill in the blanks with a word or phrase from the list above. Make necessary changes. After you finish, highlight the blanks to reveal the hidden answers.
1. I don't think you quite understand the severity of your father's health problems.
2. The spacecraft and its crew were miserably incinerated by the billion-degree temperatures generated by the fireball.
3. Several local officials are in jail on charges of colluding with the gangsters.
4. Serious conflagration was under way, which was not extinguished until about one-third of the city, including several of its historic buildings, had been destroyed.
5. In the face of severe opposition and unrelenting criticism, the task seemed overwhelming.
6. Numerous African countries have put their faith and trust in the United States to support this initiative over the long haul.
編譯：外語教學暨資源中心 編輯小組
|
Read more on VOA.
